The expression “orotracheal tube” generally designates an endotracheal tube that is inserted through the mouth. Orotracheal intubation consists in inserting a tube through the mouth, the laryngeal inlet and into the trachea of a patient. This procedure is commonly performed in medical conditions in patients who are unable to protect their airways, are at risk of pulmonary aspiration and those that require assistance with mechanical ventilation. It is also commonly performed to permit safe general anaesthesia to enable mechanical ventilation during surgery.
A laryngoscope assists with intubation by allowing the clinician to visualise the path of the endotracheal tube as it passes through the glottis towards the trachea. Tracheal intubation can be performed by direct laryngoscopy or indirect laryngoscopy.
During direct laryngoscopy, a laryngoscope is used to obtain a direct view of the vocal cords. An orotracheal tube is inserted under direct vision through the vocal cords normally in an unconscious patient. A laryngoscope typically comprises a handle and a blade. There are many types of laryngoscopes designed for direct laryngoscopy. The blade may be curved (e.g. the Macintosh blade), straight (e.g. the Miller blade) or may comprise a moveable hinged blade tip (e.g. McCoy laryngoscope).
The technique of orotracheal intubation begins with the blade inserted into the right corner of the patient's mouth. The blade is shaped such that a flange will push the tongue to the left side of the oropharynx to create space in the oropharynx through which a view of the larynx will be sought. The epiglottis is visualised. The laryngoscope handle is manipulated so that the blade lifts the epiglottis directly with the straight blade or indirectly with the curved blade thereby exposing the laryngeal inlet in normal patients. The endotracheal tube is then advanced past the vocal cords into the trachea.
Most intubations are straightforward using the direct laryngoscopy procedure described above. However some patients are known to be difficult to intubate under direct laryngoscopy, especially if there are anatomical abnormalities or if the larynx lies particularly anteriorly. Other patients are unexpectedly found during direct laryngoscopy to be difficult to intubate this way.
Intubation of these patients may be more successful using indirect laryngoscopy. This can be performed using a videolaryngoscope such as those sold under the trademarks Airtraq and GlideScope. These videolaryngoscopes have a light source and imaging modality embedded in or inserted near to the distal portion of the blade. The blade is shaped such that with manipulation the imaging modality can be positioned adjacent to the larynx. This enables visualisation of the laryngeal inlet on a viewer or screen. Fibreoptic intubating laryngoscopes are also used for intubation, particularly if direct laryngoscopy is judged to be difficult or dangerous.
When the user attempts to insert an endotracheal tube, the tip can be visualised on the screen as it passes through the larynx. It is common however with videolaryngoscopes for a good laryngoscopic view on the screen to be achieved but for the user to have difficulty directing the endotracheal tube into the laryngeal inlet. Most problematic is the endotracheal tube tip directing too posteriorly. A stiff introducer or bougie can be inserted into the endotracheal tube to try to overcome this difficulty but this adds complexity and risk to the procedure.
Some videolaryngoscopes, for example the Airtraq® and the Pentax-AWS®, have an insertion technique completely different to that used in direct laryngoscopy and have an open sided rigid channel to help guide the tube. A disadvantage of these rigid open sided channels is that the endotracheal tube is not placed with a technique similar to direct laryngoscopy which is familiar to all anesthesiologists. Another disadvantage is that depending upon tube diameter used, the tube tip is not always gripped sufficiently to direct it along the blade in a sufficiently anterior direction. Another disadvantage is that the rigidity of the guiding channel can impede the removal of the laryngoscope over the endotracheal tube when intubation has been achieved and the laryngoscope needs to be removed.
It is an object of this invention to mitigate problems such as those described above.